Coupling device for polymeric pipes

ABSTRACT

The present invention relates to a pipe coupling of the type where a pipe is freely insertable into the coupling and where a nut causes engagement of a grip ring and gasket with the pipe to provide a seal between the coupling and the pipe, and where within the coupling there is disposed a stop to indicate to a user inserting the pipe freely that the pipe has been inserted to its required location. The stop is located at a position where there is room beyond the stop for the pipe to move into. Tightening of the nut causes the pipe to move further into the coupling beyond the stop. This solves the problem of the pipe being inserted too deeply into the coupling and being deformed when the nut is tightened further.

[0001] Coupling for engagement of polymeric pipes where the pipe isinserted into a coupling to a first position and where tightening of thecoupling causes the pipe to be drawn further into said coupling.

[0002] In particular this invention relates to a coupling that issuitable for engaging the outer surface of a polymeric pipe and where apipe is inserted into an already assembled coupling. Provided in thecoupling is a first stop indicating to a user that a pipe has beensufficiently inserted into the pipe, there remaining sufficient space toaccommodate further movement of the pipe under tightening of thecoupling nut.

BACKGROUND OF THE INVENTION

[0003] Polymeric pipe couplings are well known and typically include abody, nut, and grip ring. A pipe is inserted into the body. Tighteningof the nut compresses the grip ring that in turn engages the pipe.Further tightening of the nut causes urging of the pipe further into thebody. A typical coupling was described and illustrated in our U.S. Pat.No. 5,593,186 entitled “Coupling for Outer Surface Engagement ofPolymeric Pipe”. The described coupling is adapted for engagement withthe outer surface of a polymeric pipe. The coupling includes asub-assembly of a compression sleeve, a resilient gasket ringpermanently attached to the inner end of the compression sleeve, agripping member, and a nut. The gasket ring encounters an abutment in asocket in the body as the nut is tightened, and further tightening ofthe nut radially compresses the gripping member so that its inwardlydirected barbed projections engage the outer surface of a pipe to whichthe coupling is attached. The end of the pipe is freely insertablethrough the gripping member and sleeve and into the socket in the body.There are also provided abutment surfaces within the body coupling andthe nut that abut inner and outer surfaces of a flange outstanding fromthe outer end of the compression sleeve. Also disclosed is an embodimentwith a transition spigot having a barbed tail inserted into an end of apipe enabling the coupling to accommodate a range of similar butdifferent diameter pipes.

[0004] The coupling described in the aforesaid specification and otherearlier couplings have proven to be very successful, both technicallyand commercially. Failure is almost unknown and in some areas of theworld fittings made in accordance with that specification have achievedgreat success.

[0005] A practical problem which is frequently encountered withcouplings made in accordance with said U.S. Pat. No. 5,593,186 (andother fittings having in common a gripping member and a tightening nut),is that when the nut has been partially tightened it radially compressesthe gripping member causing the inwardly directed barbed projections toengage the outer surface of a pipe to which the coupling is attached.Further tightening of the nut then results in the pipe being urged inthe direction of the nut travel along its longitudinal axis due to theforce exerted on the pipe by the barbed projections. But, because thepipe is typically inserted into the coupling until its end abuts againstan abutment surface, there is no additional room for the pipe to moveinto. As the nut is further tightened, the pipe is subject tosignificant forces that result in its deformation and leads to changesin the flow of the fluid through the pipe. Further, the rotation of thenut requires more and more torque to effect the appropriate compressionon the seal, and at times, it may be incorrectly assumed that the nut isfully tightened due to the resistive forces of pipe leading to couplingsthat leak.

[0006] It is therefore an object of the present invention to provide fora coupling whereby when the pipe is inserted into the coupling it iscaused to be held at a first location, and whereby when the coupling nutis further tightened the pipe is caused to be drawn further towards asecond location.

[0007] It is a further object of the present invention to provide for acoupling that allows manual insertion of the pipe and that prevents thepipe from being inserted too far into the coupling.

[0008] There is currently no known prior art to the applicant whereby apipe is caused to abut a coupling at a first location and wherebyfurther tightening of the coupling nut will cause the pipe to be drawntowards a second location.

BRIEF SUMMARY OF THE INVENTION

[0009] Therefore in one form of the invention there is proposed a pipecoupling including:

[0010] a body having an external thread and annular inner surfacesdefining a socket within the body of larger outer diameter at an outerend than at an intermediate location of said socket;

[0011] a stop extending at least partially around the annular innersurface in the intermediate location of said socket at a position offsetfrom the end of said intermediate location where the end is distal fromsaid outer end;

[0012] a nut having an internal thread at an inner end thereof engagingsaid body external thread, an inwardly facing abutment surface betweenends of said nut, and an outwardly converging internal circular surfacebetween said abutment surface and an outer end of said nut;

[0013] an annular sleeve having an abutment surface at is outer endco-operable with said nut abutment surface, and a resilient gasketsecured to its inner end;

[0014] a deformable gripping member having an outwardly converging outersurface complementary to said outwardly converging internal nut surface,the gripping member having an internal surface with barbs extendingradially inwardly therefrom;

[0015] internal diameters of said socket inner end, sleeve and grippingmember all being slightly greater than an external diameter of a pipe towhich said coupling is securable, such that an end of said pipe isfreely insertable through said gripping member and into said socketintermediate part until it abuts the stop, and tightening of said nutover said external thread causes axial movement of said gasket ring,sealable engagement of said gasket ring and said body, radially inwarddeformation of said gripping member such that the said barbs clamp saidpipe, and axial movement of said pipe over the stop and towards the endof said intermediate location.

[0016] The use of the stop assists in properly coupling the pipe. A userinserts the pipe into the coupling to a location where they can feelresistance to the pipe moving further into the coupling. This positionthen still provides the pipe with room to move inwardly into the pipe asit does when the nut is tightened. In this way, since the pipe is notinserted too deeply into the coupling its end is not caused to deformunder tightening of the nut.

[0017] Preferably the stop is an annular abutment surface extendingcircumferentially around the annular inner surface.

[0018] Preferably the stop is a plurality of projections positionedcircumferentially and symmetrically around the inner annular surface.

[0019] In preference there are at least three projections disposed 120degrees angularly to each other. Preferably the height of theprojections is at least equal to the thickness of the pipe.

[0020] In preference the projections are wedge shaped projections whoselongitudinal direction extends in the longitudinal direction of thecoupling.

[0021] Preferably the front surface of the wedge facing the outer end isdisposed at an angle other than a right angle but greater than 45degrees to the longitudinal axis.

[0022] Preferably the front surface has at least two faces whose angleto the longitudinal axis is less than 90 degrees.

[0023] Advantageously the projections are wedge shaped projections whoselongitudinal direction extends generally perpendicular to thelongitudinal direction of the coupling.

[0024] Advantageously the wedge shaped projections are of an arcuateshape.

[0025] In a further form of the invention there is proposed a pipecoupling of the type where a pipe is freely insertable into the couplingand including:

[0026] a body having annular inner surfaces and external threads;

[0027] a nut having internal threads adapted to engage said body;

[0028] a grip ring disposed within the body and of a shape andconfiguration that rotation of the nut causes it to move in both theaxial and longitudinal direction, said nut having projections adapted toengage said pipe when the nut is tightened and having an end adapted toengage a gasket and move it into a sealing cavity when the nut istightened, wherein said body includes an abutment surface located at aposition away form the ends of said body to provide a guide to the userwhen inserting the pipe freely into the coupling and where the abutmentsurface is of a shape and configuration such that under rotation of thenut the pipe is caused to move over said abutment surface and furtherinto said coupling.

[0029] Thus the present invention provides for an improved pipe couplingwhere there is a mechanism to indicate to a user that a pipe as beensufficiently inserted into the coupling whilst there still remainingroom for the pipe to move axially inwardly into the coupling as it doesunder the forcing of the grip ring.

[0030] The typical coupling to which the present invention can beapplied includes a gripping member and a sub-assembly of a compressionsleeve and resilient gasket ring generally attached to the inner end ofthe compression sleeve. A pipe end is freely insertable through thesub-assembly and into a socket in the body of the coupling abuttingagainst a pipe abutment surface or stop. The gasket ring encounters anabutment in its socket in the body as the nut is tightened, whereintightening of the nut radially compresses the gripping member so thatits inwardly directed barbed projections engage the outer surface of apipe to which the coupling is attached. When the barbs have engaged thepipe, further tightening of the nut causes the pipe to be forcedinwardly into the coupling past the pipe abutment surface and towards anabutment shoulder. The longitudinal distance between the pipe abutmentsurface and the abutment shoulder is generally equal to or greater thanthe longitudinal travel of the nut from the position at which the barbedprojections have gripped the pipe to the final tightened position of thenut. There are also provided abutment surfaces within the body of thecoupling or the end of the body, and the nut, that abut inner and outersurfaces of a flange outstanding from the outer end of the compressionsleeve.

BRIEF DESCRIPTION OF TEE DRAWINGS

[0031] The accompanying drawings, which are incorporated in andconstitute a part of this specification, illustrate severalimplementations of the invention and, together with the description,serve to explain the advantages and principles of the invention. In thedrawings,

[0032]FIG. 1 is a central elevational section that shows a pipe endinserted through a sub-assembly comprising a nut, gripping member andsleeve, and into a socket in the body of a fitting before the nut beingtightened;

[0033]FIG. 2 is a similar section showing the configuration ofcomponents and location of the pipe when the nut is tightened onto thebody;

[0034]FIG. 3 is a central elevational section showing a dual pipecoupling wherein one side the nut has been tightened and on the otherbefore being tightened;

[0035]FIG. 4 is a partial perspective cut-away view of a pipe abutmentsurface according to a first embodiment of the invention;

[0036]FIG. 5 is a partial perspective cut-away view of a pipe abutmentsurface according to a second embodiment of the invention;

[0037]FIG. 6 is a partial perspective cut-away view of a pipe abutmentsurface according to a third embodiment of the invention;

[0038]FIG. 7 is a detailed view of the pipe abutment surface of FIG. 6;

[0039]FIG. 8 is a partial perspective cut-away view of a pipe abutmentsurface according to a fourth embodiment of the invention; and

[0040]FIG. 9 is a cross-sectional view of one of the projections of FIG.8.

DESCRIPTION OF THE PREFFERED EMBODIMENT

[0041] The following detailed description of the invention refers to theaccompanying drawings. Although the description includes exemplaryembodiments, other embodiments are possible, and changes may be made tothe embodiments described without departing from the spirit and scope ofthe invention. Wherever possible, the same reference numbers will beused throughout the drawings and the following description to refer tothe same and like parts.

[0042] There is shown in FIG. 1 a coupling with an inserted pipe beforetightening of the nut. The coupling 10 that engages the outer surface ofpipe 12 includes a body 14 that has a pipe abutment surface 16 which isabutted by the end of the pipe 12 when inserted into the coupling asshown in FIG. 1. The body includes a further shoulder 18 whose diameteris smaller than that of the pipe abutment surface 16.

[0043] The body 14 has a male thread 20, and between the outer end 22 ofthe body and the shoulder 18 is a generally annular planar surface 24which constitutes an abutment surface of a socket or cavity 26 for aresilient gasket ring 28, abutment shoulder 18 of the socket 26 beingthe inner end of the socket, the socket 26 also having two cylindricalintermediate and axially outer walls 30 and 32 separated by a step 34(three diameters in all), the diameter of the outer wall 30 exceedingthat of the inner wall 32.

[0044] Surrounding the pipe 12 is a compression sleeve 36, which carriesthe resilient gasket ring 28 on its inner end, being fused, bonded, orotherwise affixed to the end of the compression sleeve 36. This couldalternatively be engaged by a mechanical tongue and groove or otherwiseaffixed on the face end of the sleeve 36, and the outer diameter ofgasket ring 28 is less than the diameter of outer wall 32 but greaterthan the diameter of intermediate wall 30, so that the compressionsleeve can be readily inserted into the body 14 with the gasket ring 28being freely movable adjacent wall 32 but requiring compression by axialmovement of compression sleeve 36 to enter socket 26.

[0045] Adjacent but axially outwardly of sleeve 36 is a gripping member38 having radially inwardly but axially spaced barb projections 40, andhaving an outwardly converging tapered surface 42. The gripping member38 must be radially deformable, and thereby circumferentiallydeformable, and is typically a split ring.

[0046] The nut 44 is provided with a tail 46 having an outwardlyconverging inner tapered surface 48 the included angle of which isapproximately the same as the tapered surface 42 of the gripping member38, and inwardly from the outer end of tail 46 there is an annularplanar shoulder 50 which, upon tightening of the nut 44, will bearagainst end surface 52 of compression sleeve 36.

[0047] The annular surface 54 of the flange at the outer end of sleeve36 is spaced axially inwardly a short distance from the surface 52.

[0048] When the pipe 12 is inserted into the socket 26 of the couplingas shown in FIG. 1, it abuts against the pipe abutment surface 16.Initial tightening of the nut 44 on the body 14 will not cause abutmentof shoulder 50 with annular surface 52 of the sleeve 36. The inner endof the gripping member 38 is loosely contained within a recess 56 in theouter end of sleeve 36, and the gasket ring 28, sleeve 36, and grippingmember 38 move in together with the nut 44 since there is a clearance ofall portions of the coupling around the polymeric pipe 12 when it isfirst inserted. However, after the nut 44 travels a short axial distanceinwardly the gasket ring 28 is intercepted by the step 34 and will notpass that step until compressed. Continued movement of the nut thereforecauses a small axially inward movement of the sleeve 36 and the grippingmember 38, and must be accommodated by the sliding of inner surface 48over the outer tapered surface 42, in turn causing the barb projections40 of the gripping member 38 to engage the outer surface of pipe 12.

[0049] When the barb projections 40 have engaged the pipe, furthertightening of the nut 44 causes the pipe 12 to be forced inwardly intothe body 14. The longitudinal forces are such that the end of the pipe12 that abuts abutment surface 16 is compressed and/or deformed so thatit travels past surface 16 towards shoulder 18.

[0050] Tightening of the nut 44 (generally by rotation in the clockwisedirection) also brings the shoulder 50 into abutment with the annularsurface 52 of compression sleeve 36 and progresses the sleeve 36 axiallyinwardly, causing sufficient compression of the gasket ring 28 for it toenter the inner smaller diameter intermediate portion 32 of the socket26. The socket is of such dimension that the gasket ring 28 effects asatisfactory seal between the body 14 and the pipe 12, and this isfurther enhanced when the nut 44 is fully tightened so that the twosurfaces of the sleeve 36 respectively lie in abutment with the outerend 22 of the body 14 and the shoulder 50 as shown in FIG. 2. At thislocation, compression of the resilient gasket ring 28 results in a seal,which is effective against very high pressures.

[0051] Since the nut cannot be progressed any further inwardly, thecompression of both the rings 28 and 38 is controlled to lie within therange dictated by the diameter of the pipe 12. In addition, thelongitudinal distance 66 between the abutment surface 16 and shoulder 18is generally equal to or longer than the longitudinal travel of the nutwhen the barbed projections have first gripped the pipe.

[0052] If the pipe 12 is not inserted into the body 14 and the nut 44 isscrewed forwardly, the pipe 12 will not be able to be forced inwardly tothe body 14 unless the nut is screwed back to its loose state.

[0053] When the nut 44 is screwed back (usually rotation anti-clockwise)the compression sleeve 36 is also pulled back (rearwardly) due to aloose engagement of the reverse tapered surfaces 58 of compressionsleeve 36 and 60 of nut 44, and subsequent abutment of compressionsleeve 36 against inner end of gripping member 38. Because the gasketring 28 is attached to the inner end of sleeve 36 that is also withdrawnand does not remain in the small diameter portion of socket 26.

[0054] As illustrated in FIG. 2, when sleeve nut 44 is tightened overbody 14, radially outstanding flange 62 of gripping member 38 liesadjacent shoulder 64 of nut 44. If a tensile load is applied to pipe 12,and body 14 is fixed, any relative movement will initially impart moreradial compression to gripping member 38, but such movement (if any)will be very small, and will be resisted by abutment of flange 62against shoulder 64.

[0055] Simultaneously, as the sleeve 44 is being tightened and theprojections 40 engage the pipe the pipe end 65 is forced past theabutment surface 16 towards shoulder 18. When the pipe 12 is beingmanually inserted it therefore allows the user to appreciate that thepipe is in the correct position within the body 14 whilst there stillbeing sufficient room for further travel of the pipe inwardly due to thetightening of the nut.

[0056] It will be appreciated that the assembly may be sold with thecomponents in place and held captive while nevertheless retaining aclearance over the outer surface of pipe 12.

[0057] Illustrated in FIG. 3 is a two-pipe coupling, where the couplingmay be used to join two pipes together. As seen in that Figure, the lefthand side of the coupling 10 a has had a pipe inserted and the nut 44 isyet to be tightened with the end of the pipe 65 a abutting surface 16,whilst the end of the other pipe 65 b has had the pipe inserted and thenut 44 fully tightened whereupon the pipe end 65 b has moved pastshoulder 16 and towards the abutment surface 18. In this embodiment, thedistance 66 between the surface 16 and the shoulder 18 is generallygreater than or equal to the longitudinal travel of the nut 44 when thebarbed projections 40 have engaged the pipe 12. Thus when the nut 44 isfully tightened the pipe 12 is positioned generally against or adjacentshoulder 18.

[0058] As illustrated in FIG. 4 where there is shown a cut-away partialperspective view of the body 14, the abutment surface 16 may be anannular step where the distance 66 between the surface 16 and shoulder18 is greater to the full travel of the nut. It has also been discoveredthat the annular step angle to the longitudinal axis of the body may bea right angle for when being tightened the nut produces sufficientlongitudinal force that the pipe is forced even beyond the right angle.However, those skilled in the art will appreciate that the angle may beless than 90 degrees, provided that when the pipe is manually inserted,the user feels sufficient resistance to assume that the pipe has beeninserted sufficiently deeply into the body.

[0059] Of course, those skilled in the art will readily appreciate thatthe pipe abutment surface need not be a solid annular ring asillustrated in FIG. 4, but could equally well be a plurality ofprojections symmetrically circumferentially disposed within the body 14and positioned before the abutment surface 18. This is illustrated inFIG. 5 where the abutment surface 16 is defined by three wedges 68located at 120-degree intervals within the body of the pipe. The lengthof the wedges is equal to the length 66 being equal to or greater thanthe travel of the nut when fully tightened.

[0060] Whilst FIGS. 4 and 5 illustrated the abutment surface having agenerally right angle to the longitudinal axis of the body, the frontface 67 of the wedges may be tapered to enable for easier movement ofthe pipe towards the shoulder 18 when the nut is being tightened. Theangle has to be chosen so that when the pipe is being manually insertedit is not easily possible to push the pipe past the faces 67 so that theuser feels as if the pipe has been sufficiently inserted into the body.However, it has been discovered that even angles of around 45 degreesare sufficiently steep to provide an abutment surface 16 against which apipe abuts when manually inserted. Thus, as illustrated in thisembodiment the surface 67 includes two faces 67 a and 67 b whose apex 67c is at an angle of some 70 degrees to the longitudinal axis of thebody.

[0061] It is to be understood that where the abutment surface 16 isdefined by individual projections, the number of projections is notnecessarily three, and there may be more projections. In addition, insuch an arrangement, the angle of the front faces of the wedges thatdefine the surface 16 may vary for different projections. Thus some ofthe projections may be right-angled whilst other at a much gentlerangle. The body of the pipe between the surface 16 and shoulder 18 mayalso be of a non-smooth configuration to assist in preventing the pipefrom rotational motion when the nut is being tightened.

[0062] Another alternative embodiment includes varying the total lengthor orientation of the projections. Referring now to FIG. 8, there isshown a plurality of projections 70 at right angles to the longitudinalaxis of the body. The projections are preferably hump or arcuate shapein their cross-section, as shown in FIG. 9, the configuration being suchthat a pipe will still abut against the projections when manuallyinserted but will still enable the pipe to pass the projections whenunder the force exerted by tightening of the nut.

[0063] Some of the projections 70 may not extend all the way to theshoulder 18 so that when the pipe reaches the shoulder it expandsoutwardly and springs back into its natural shape. Similarly, with asolid annular abutment surface as illustrated in FIGS. 1 and 2, thediameter of the pipe 12 between the surface 16 and the shoulder 18 maybe equal to that before the shoulder. Thus when the pipe has been forcedpast the surface 16 its diameter increases so that the end of the pipeis not caused to deform to the same degree.

[0064] Those skilled in the art will readily appreciate that there aremany alternative constructions of surface 16. As discussed above it maybe formed by a annular shoulder in the body of the coupling or byincluding discrete projections whose size, shape and orientationprovides a sufficient surface area so that when a user inserts a pipeinto the body they know that they have inserted the pipe as far isnecessary whilst there still being sufficient room to accommodatefurther movement of the pipe into the coupling when tightening of thenut.

[0065] It is also to be understood whereas the above descriptiondiscussed a coupling having a particular configuration it is notintended to limit the present invention to such a coupling and otherpipe couplings may includes the present invention. For example, thepresent invention may equally well be applied in a coupling as definedin Applicant's Australian Patent 707930. In that invention, the sleeveof the coupling is dispensed with and a spigot includes an annularflange that acts on the gasket to provide a seal under tightening of thenut. The abutment surfaces the subject of the present invention couldvery well be located on the spigot so that the pipe can still moveaxially inwardly.

[0066] It is therefore intended that the present invention can beapplied to all pipe couplings of the type where a nut is used to drive agrip ring that in turn engages and axially forces the pipe further intothe body of the coupling. The present invention thus solves the problemof the end of such a pipe being deformed due to no remaininglongitudinal space for the pipe to travel through.

[0067] Whilst the foregoing description has set forth the preferredembodiments of the present invention in some detail, it is to beunderstood that numerous modifications, obvious to a person skilled inthe art, may be made without departing from the scope of the invention.It is therefore to be understood that the invention is not limited tothe specific embodiments as herein described.

1. A pipe coupling including: a body having an external thread andannular inner surfaces defining a socket within the body of larger outerdiameter at an outer end than at an intermediate location of saidsocket; a stop extending at least partially around the annular innersurface in the intermediate location of said socket at a position offsetfrom the end of said intermediate location where the end is distal fromsaid outer end; a nut having an internal thread at an inner end thereofengaging said body external thread, an inwardly facing abutment surfacebetween ends of said nut, and an outwardly converging internal circularsurface between said abutment surface and an outer end of said nut; anannular sleeve having an abutment surface at is outer end co-operablewith said nut abutment surface, and a resilient gasket secured to itsinner end; a deformable gripping member having an outwardly convergingouter surface complementary to said outwardly converging internal nutsurface, the gripping member having an internal surface with barbsextending radially inwardly therefrom; internal diameters of said socketinner end, sleeve and gripping member all being slightly greater than anexternal diameter of a pipe to which said coupling is securable, suchthat an end of said pipe is freely insertable through said grippingmember and into said socket intermediate part until it abuts the stop,and tightening of said nut over said external thread causes axialmovement of said gasket ring, sealable engagement of said gasket ringand said body, radially inward deformation of said gripping member suchthat the said barbs clamp said pipe, and axial movement of said pipeover the stop and towards the end of said intermediate location.
 2. Apipe coupling as in claim 1 wherein the stop is an annular abutmentsurface extending circumferentially around the annular inner surface. 3.A pipe coupling as in claim 1 wherein the stop is a plurality ofprojections positioned circumferentially and symmetrically around theinner annular surface.
 4. A pipe coupling as in claim 3 where there areat least three projections disposed 120 degrees angularly to each other.5. A pipe coupling as in claim 3 or 4 wherein the projections are wedgeshaped projections whose longitudinal direction extends in thelongitudinal direction of the coupling.
 6. A pipe coupling as in claim 5wherein the front surface of the wedge facing the outer end is disposedat an angle other than a right angle but greater than 45 degrees to thelongitudinal axis.
 7. A pipe coupling as in claim 6 wherein the frontsurface has at least two faces whose angle to the longitudinal axis isless than 90 degrees.
 8. A pipe coupling as in claim 3 or 4 wherein theprojections are wedge shaped projections whose longitudinal directionextends generally perpendicular to the longitudinal direction of thecoupling.
 9. A pipe coupling as in claim 8 wherein the wedge shapedprojections are of an arcuate shape.
 10. A pipe coupling of the typewhere a pipe is freely insertable into the coupling and including: abody having annular inner surfaces and external threads; a nut havinginternal threads adapted to engage said body; a grip ring disposedwithin the body and of a shape and configuration that rotation of thenut causes it to move in both the axial and longitudinal direction, saidnut having projections adapted to engage said pipe when the nut istightened and having an end adapted to engage a gasket and move it intoa sealing cavity when the nut is tightened, wherein said body includesan abutment surface located at a position away form the ends of saidbody to provide a guide to the user when inserting the pipe freely intothe coupling and where the abutment surface is of a shape andconfiguration such that under rotation of the nut the pipe is caused tomove over said abutment surface and further into said coupling.